Gran Turismo has always focused on the unadulterated beauty of the cars, and after experiencing a high speed accident (scroll down to “Gran Turismo Behind the Scenes”) there's no wonder why extensively modelling damage would be the last thing … I want a damage mode where at least the car is limited in speed and behaves strangely and needs to go in to the pit for repairs. …. That's a funny excuse for justifying the lack of serious damage model, not that I mind. …

Read this article:
Damage Modelling in Gran Turismo 6 “Similar to GT5″ – GTPlanet